Heterodyne receiver



Patented Apr. 2, 1940 UNITED STATES PATENT ori-icty HETERODYNE RECEIVER Application October 6, 1937, Serial No. 167,519

Germany October 7, 1936 1 Claim.

The reception of short waves is in general on the heterodyne principle, that is to say, the received frequency is superimposed on a. second frequency while the intermediate or beat frequency thus produced is amplified and rectified.

In the reception of short waves the beat frequency employed is in general a constant frequency that belongs to the range of the mean waves that is, between short waves and long waves. For instance, a wave of some 100 meters is used with a reception of waves of 50 meters. It is' well-known to employ the beat frequency part for the reception of waves of the mean range. To such end means is provided to change from short waves to long waves in such a manner that in the case of a short-wave reception a heterodyning arrangement is used while with long-wave reception the beat frequency part of the short-wave receiver is employed. 20 In arrangements as provided by the invention a heterodyne receiver while receiving short waves is at the same time in readiness for the reception of a second wave. This second wave may serve for the reception of distress signals, for example. Distress signals are in general given on a wave of 600 meters. It has been customary to have an additional receiver kept in readiness for receiving these signals. The invention does away with such second receiver, and thus avoids a separate attendance, by arranging to have the beat frequency part of a short-wave receiver in constant readiness of reception as regards distress signals, the attendant to this receiver thus also attending to the distress call receiver. 35 The invention will be understood from the following description and be pointed out particularly in the appended claim, reference being had to the accompanying drawing in which Fig. 1 is a wiring diagram representing one embodiment of the invention, Fig. 2 is a wiring diagram showing a modication of the device illustrated in Fig. 1.

A short-wave receiver, connected to an antenna A by an inductive coupling 4, comprises a heterodyning part l, in which the received fre- (CL o- 20) quency is amplified and superimposed with another frequency, and also comprises a beat frequency part 2 in which the intermediate or beat frequency produced in part l is amplified and rectified.

In accordance with the invention the beat frequency is preferably made to accord with that frequency for which an additional readiness for reception is to be provided. Part 2 is connected to antenna A by an inductive coupling 5, in such a manner as to prevent the short waves received over coupling transformer 4 from being fed back to antenna A over transformer 5.

In the arrangement shown in Fig. 1, such back coupling is avoided by a rejector device 3, while in the arrangement represented in Fig. 2 the antenna A is connected to beat frequency part 2 behind the first or input stage thereof.

It will thus be seen that with short-wave reception there is also a readiness to receive a frequency that equals the constant beat frequency. Whenever a distress call arrives the attendant may disconnect ,the heterodyne part l and receive this call.

What is claimed is:

A radio receiving arrangement for receiving waves' of different frequencies comprising an antgma, a superheterodyne receiver having a mquency converting part for producing a beat frequency from one of said received waves, means to 1 rt to said antenna, and a beat frequency amp i er p coupled to the output of said converter part, a

v circuit also connecting the input side of said amplier-rectier part to said antenna for direct reception of waves of the frequency of said beat frequency, said circuit including coupling means separate from the first mentioned coupling means whereby energy from said converter tends to feed back to said antenna, and a rejector circuit interposed between the last mentioned coupling means and the amplifier-rectifier, part to prevent feedback from the output of said converter part to said antenna..

ERNST KRAMAR. 

